Distinct structures of coordination polymers incorporating flexible triazole-based ligand: topological diversities, crystal structures and property studies

Six new coordination polymers, namely {[Zn(btec)(0.5)(btmb)]·2H(2)O}(n) (1), {[Co(btec)(0.5)(btmb)(H(2)O)]·3H(2)O}(n) (2), {[Cu(btec)(0.5)(btmb)]·H(2)O}(n) (3), {[Cu(4)(btc)(4)(btmb)(4)]·H(2)O}(n) (4), {[Co(3)(bta)(2)(btmb)(2)]·2H(2)O}(n) (5), [Co(Hbta)(btmb)](n) (6) (H(4)btec = 1,2,4,5-benzenetetracarboxylate, H(3)btc = 1,3,5-benzenetricarboxylate, H(3)bta = 1,2,4-benzenetricarboxylate and btmb = 4,4'-bis(1,2,4-triazol-1-ylmethyl)biphenyl), have been successfully synthesized under hydrothermal conditions. All these complexes were structurally determined by single-crystal X-ray diffraction, elemental analysis, IR, TGA and XRD. Crystal structural analysis reveals that 1 is the first example of an unusual 3D framework with (8(6)) topology containing a 2D molecular fabric structure. Complex 2 exhibits a 3D NbO network with (6(4)·8(2)) topology. In 3, Cu(II) ions are coordinated by anti-conformational btmb ligands to form left- and right-handed double helices, which are further bridged by the 4-connected btec(4-) anions to give a 3D porous network. Complex 4 presents a rare 3D gra network structure with (6(3))(6(9)·8) topology. 5 and 6 were obtained through controllable pH values of solution, 5 features a scarce binodal (3,8)-connected tfz-d framework with the trinuclear Co(II) clusters acting as nodes, whereas 6 has an extended 2D 4(4) grid-like layer and the adjacent 2D layers are interconnected by strong hydrogen bonding interactions into a 3D supramolecular framework. The structural diversities indicate that distinct organic acid ligands, the nature of metal ions and the pH value play crucial roles in modulating the formation of the resulting coordination complexes and the connectivity of the ultimate topological nets. Moreover, magnetic susceptibility measurement of 5 indicates the presence of weak ferromagnetic interactions between the Co(II) ions bridged by carboxylate groups.     

New two-dimensional metal-organic networks constructed from 1,2,4,5-benzenetetracarboxylate and chelate ligands

Two novel nickel coordination polymers [Ni(2)(2,2'-bipy)(2)(OH)(2)(H(2)btec)](3)(n)(1) and [Ni(2)(1,10'-phen)(2)(H(2)O)(2)(btec)](n)(2) (btec = 1,2,4,5-benzenetetracarboxylate) have been hydrothermally synthesized and characterized by elemental analyses, IR and XPS spectra, TG analysis, X-ray powder diffraction, and single crystal X-ray diffraction. Crystal data for 1: C(90)H(66)N(12)O(30)Ni(6), monoclinic P2(1)/c, a = 10.905(2) A, b = 18.006(4) A, c = 20.551(4) A, beta = 94.91(3) degrees, Z = 2. Crystal data for 2: C(34)H(22)N(4)O(10)Ni(2), monoclinic P2(1)/n, a = 10.122(2) A, b = 9.3106(19) A, c = 15.690(3) A, beta = 92.03(3) degrees, Z = 2. Compound 1 exhibits a novel one-dimensional chainlike structure, in which the dinuclear Ni centers are linked by the btec ligands. Furthermore, the adjacent chains are linked into a 2-D wavelike layer via the strong OH.O hydrogen bonding interactions. Compound 2 possesses an unusual two-dimensional steplike network with interesting rhombic grids. Both compounds exhibit unprecedented metal-organic ligand construction modes in [M/btec/L] (M = transition metal; L = chelate ligands) systems. The magnetic behaviors of compounds 1 and 2 have been studied.     

Co-ligand-directed structural and magnetic diversities in an anisotropic Co(II)-triazolate system

Three novel 3,5-diamino-1,2,4-triazole (Hdatrz)-based Co(II) coordination complexes, [Co(Hdatrz)(0.5)(H(2)O)(2)(btec)(0.5)](n) (1), {[Co(Hdatrz)(Hbtc)]·H(2)O}(n) (2) and [Co(2)(datrz)(2)(nb)(2)](n) (3) (H(4)btec = 1,2,4,5-benzenetetracarboxylic acid, H(3)btc = 1,3,5-benzenetricarboxylic acid and Hnb = 4-nitrobenzoic acid), were synthesized by incorporating different carboxylate-containing co-ligands and then were structurally and magnetically characterized. Complex 1 is a 3D pillared-layer framework with corrugated Co(II)-btec(4-) layers supported by neutral μ(2)-N1, N4-Hdatrz ligands. In contrast, the other two complexes are chiral (4, 4)- and racemic (4, 8(2))-topological layers with asymmetric μ(2)-N1, N4-Hdatrz-bridged helical chains extended by bis-monodentate Hbtc(2-) ligands for 2 and with a μ(3)-N1, N2, N4-datrz((-)) aggregated Shastry-Sutherland magnetic layer for 3. More interestingly, different magnetic phenomena with a field-induced metamagnetic transition from antiferromagnetic ordering to a ferromagnetic state for 1, spin-canted antiferromagnetism with a T(N) lower than 2.0 K for 2, as well as the coexistence of spin frustration and spin-flop transitions for 3 were observed, which, significantly, are governed by the local low-dimensional magnetic motifs mediated by the carboxylate and/or triazolate heterobridges in the anisotropic Co(II)-triazolate system.     

Synthesis and Crystal Structure of a New Zn(Ⅱ) Coordination Polymer Constructed by 1,2,4,5-Benzenetetracarboxylate

A new Zn(Ⅱ) coordination polymer [Zn3(btec)(OH)2(H2O)2]n (1, btec = 1,2,4,5- benzenetetracarboxylate) has been synthesized by hydrothermal reaction and its structure was determined by single-crystal X-ray diffraction analysis. The title compound crystallizes in mono- clinic, space group C2/c, with a = 19.580(3), b = 5.0137(8), c = 15.975(3), β = 121.629(2)°, V = 1335.3(4)3, C10H8O12Zn3, Mr = 516.27, Z = 4, Dc = 2.568g/cm3, μ = 5.419 mm-1, F(000) = 1016, R = 0.0590 and Rw = 0.1279 for 1110 observed reflections (I > 2σ(I)). X-ray analysis shows that the asymmetric unit of the title compound contains two crystallographically unique Zn(Ⅱ) atoms which are connected through the bridging carboxylate oxygen atoms of the btec ligands and μ2-bridging oxygen atoms of water molecules to generate an infinite one-dimensional chain. The adjacent chains are linked together through the benzene rings of the btec ligands to form a two-dimensional polymeric network. The adjacent two-dimensional layers are further connected together by the benzene rings of btec ligands to give the final three-dimensional structure. The benzene rings act as pillars between two layers.     

Syntheses and characterizations of copper(II) polymeric complexes constructed from 1,2,4,5-benzenetetracarboxylic acid

Four polymeric complexes with rectangular grids or channels, [Cu2(btec)(H2O)4*2H2O]n (2), [Cu2(btec)4/4[Cu(Hbtec)2/2(4,4'-Hbpy)(H2O)2]2*4H2O]n (3), [Cu2(btec)(hmt)(H2O)4*8H2O]n (4), and [Cu3(btec)(OH)2]n (5), were designed and constructed from Cu(II) ion and 1,2,4,5-benzenetetracarboxylic acid along with auxiliary ligands (where H4btec = 1,2,4,5-benzenetetracarboxylic acid, 4,4'-Hbpy = monoprotonated 4,4'-bipyridine, and hmt = hexamethylenetetramine). Complexes 2, 3, and 4 have rectangular pores with the size of 6.5 A x 4.5 A, 6 A x 7 A, and 10.1 A x 11.8 A, respectively, while 5 has a channel of 7.4 A x 9.6 A. The complexes show interesting magnetic properties due to the different coordination modes of the carboxylate groups and the presence of auxiliary ligands. On lowering the temperature, the magnetic interactions in 2 are changed from antiferromagnetic to ferromagnetic. For 3, the antiferromagnetic interactions weaken sharply at low temperature. Complex 4 shows ferromagnetic interactions while 5 is antiferromagnetic.     

Synthesis, structures, and magnetic properties of metal-coordination polymers with benzenepentacarboxylate linkers

Three hybrid organic-inorganic coordination polymers with benzenepentacarboxylate (BPCA) linkers, [Co3(C6H(COO)5)(OH)(H2O)3] (1-Co), [Zn3(C6H(COO)5)(OH)(H2O)3] (2-Zn), and [Co5(C6H(COO)5)2(H2O)12].(H2O)12 (3-Co), were synthesized hydrothermally and were characterized structurally and magnetically. 1-Co and 2-Zn are isostructural [C2/c; Z=8; 1-Co, a=19.5350(6) A, b=10.4494(4) A, and c=13.2353(5) A, beta=97.2768(8) degrees; 2-Zn, a=19.5418(9) A, b=10.3220(10) A, and c=13.4660(10) A, beta=98.455(10) degrees] with three-dimensional structures that contain [M6] secondary building units bridged by BPCA ligands. A different cobalt-based compound, 3-Co, forms at lower pH and lower reaction temperature. Its structure [P21/c; Z=2; a=12.6162(2) A, b=11.3768(2) A, and c=15.3401(3) A, beta=91.539(1) degrees] is a more loosely packed framework with free (noncoordinated) carboxylic groups pointing at water-filled cavities in the framework. The magnetic phase diagram of 1-Co established through detailed magnetic measurements shows a metamagnetic transition below TN=3.8 K. The less-packed compound 3-Co, on the other hand, remains paramagnetic above 1.9 K. The three compounds are the first examples of coordination polymers with benzenepentacarboxylate linkers and fill the gap of coordination polymers involving benzenepolycarboxylate linkers of the general type C6H6-n(COOH)n, where n=2-6.     

Syntheses and characterizations of three-dimensional channel-like polymeric lanthanide complexes constructed by 1,2,4,5-benzenetetracarboxylic acid

The hydrothermal reaction of YbCl(3) small middle dot6H(2)O with 1,2,4,5-benzenetetracarboxylic dianhydride resulted in [[Yb((b)btec)(1/4)((d)btec)(3/6)(H(2)O)(2)](4).6H(2)O](n)() (1) (H(4)btec = 1,2,4,5-benzenetetracarboxylic acid), and the solvothermal reaction of Er(NO(3))(3) small middle dot6H(2)O or TbCl(3).6H(2)O with 1,2,4,5-benzenetetracarboxylic dianhydride in H(2)O/acetic acid gave rise to [[Er(2)((c)btec)(2/4)((e)btec)(2/4)((f)btec)(2/4)(H(2)O)(4)].4H(2)O](n)() (2) and [[Tb(H(2)btec)(2/4)((f)btec)(3/6)(H(2)O)].2H(2)O](n)() (3), respectively. Complex 1 crystallizes in monoclinic space group C2/m with a = 20.8119(5) A, b = 17.6174(1) A, c = 5.7252(2) A, beta = 92.324(1) degrees, and Z = 1. 1 possesses a three-dimensional framework consisting of eight-coordinate ytterbium centers and two kinds of channels along the c axis. Complex 2 crystallizes in triclinic space group P with a = 9.6739(5) A, b = 11.0039(5) A, c = 11.5523 A, alpha = 104.8330(10) degrees, beta = 91.0000(10) degrees, gamma = 114.2570(10) degrees, and Z = 2. 2 has a three-dimensional framework comprising both eight- and nine-coordinate erbium centers and channels along the a axis. Complex 3 crystallizes in monoclinic space group P2(1)/n with a = 10.7246(12) A, b = 7.1693(9) A, c = 17.158(2) A, beta = 97.109(2) degrees, and Z = 4. 3 shows a three-dimensional framework containing nine-coordinate terbium centers and channels along the b axis. Uncoordinated water molecules occupy the channels in the three complexes. TGA and XRPD were determined for the three complexes, and the results illustrate that the framework of 1 is retained upon removal of uncoordinated and coordinated water molecules.     

Synthesis, Crystal Structure and Characterization of a New Manganese(Ⅱ)Tetracarboxylate

By hydrothermal synthesis,a manganese(Ⅱ)tetracarboxylate [Mn(2,2'-bipyridi-ne)btec)o.5(H2O)]2n(H4btec=1,2,4,5-benzenetetracarboxylic acid)was obtained and characteri-zed by single-crystal X-ray diffraction,IR,elemental analysis and thermogravimetrie analysis.It crystallizes in triclinic,space group P(1),with a=7.721(4),b=8.905(5),c=10.712(6)(A),α=80.899(8),β=70.371(8),γ=78.201(8)°,z=2,V=675.8(7)(A)3,Mr=354.20,Dc=1.741 g/cm3,μ=1.007mm-1,F(000)=360,S=0.956,(△/σ)max=0.000,the final R=0.0490 and wR=0.1262.This compound presents an infinite 1D polymer featuring a double-chain structure.The Mn(Ⅱ)ion is five-coordinated.The four carboxylate groups of btec4- are all deprotonated and coordinated to four Mn atoms in a monodentate fashion,forming a 1D double chain structure with a cavity.Such chains are interconnected by π-π stacking interactions into 2D layers which are further interlinked into a supramolecular structure by hydrogen bonds.     

A Three-dimensional Supramolecular Complex {[Co(H2btec)(2,2'-bipy)(H2O)3]·H2O}n Assembled via Hydrogen Bonding and π-π Stacking Interactions

A new cobalt compound, {[Co(H2btec)(2,2'-bipy)(H2O)3]·H2O}n (1, H4btec =1,2,4,5-benzenetetracarboxylic acid, 2,2'-bipy = 2,2'-bipyridine), has been synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR and X-ray powder diffraction. The crystal belongs to the triclinic system, space group P-1, with a = 7.230(3), b = 11.626(5), c =14.001(6) (A), α = 108.12(0)°, β= 95.85(0)°, V= 1095.33(157)(A)3, C20H20CoN2O12, Mr= 539.31,Z=2, Dc = 1.635 g/cm3,μ = 0.855 mm-1, F(000) = 554, R = 0.0427 and wR = 0.1042 for 3883 observed reflections (Ⅰ ＞ 2σ(Ⅰ)). The title compound features a discrete molecular structure, which is connected with each other through extensive O-H…O hydrogen bonds into an intricate 3D supramolecular network. Additionally, two different patterns of π-π stacking interactions further consolidate the framework.     

Synthesis,Crystal Structure and Magnetic Properties of a Ni（Ⅱ） Supramolecular Complex Based on Aromatic Polycarboxylate Ligand

A Ni(Ⅱ) supramolecular complex,[Ni 2 (btec)(3py) 2 (H 2 O) 8 ](H 2 O) 4 (1),has been synthesized by Ni(ClO 4) 2 ·6H 2 O,benzene-1,2,4,5-tetracarboxylic acid (H 4 btec) and terminal ligand 3-hydroxypyridine (3py) in aqueous solution.The title compound crystallizes in triclinic system,space group P1,with a=8.5637(12),b=9.4138(13),c=10.3611(14),α=67.9540(10),β=85.1740(10),γ=76.9890(10)°,V=754.33(18) 3,Z=2,M r=386.96,D c=1.704 Mg/m 3,μ=1.345 mm-1,F(000)=402,the final R=0.0222 and wR=0.0563 for 2675 observed reflections with I > 2σ(Ⅰ).The adjacent discrete molecules are further self-assembled by intermolecular π-π and O-H···O hydrogen bonding interactions to construct a 3D supramolecular framework.Magnetic measurement shows weak ferromagnetic interaction in the range of 2～300 K.     

Cobalt and manganese diphosphonates with one-, two-, and three-dimensional structures and field-induced magnetic transitions

Reactions of 2-(1-Imidazole)-1-hydroxyl-1,1'-ethylidenediphosphonic acid (ImhedpH(4)) and cobalt or manganese salts under hydrothermal conditions result in three new metal diphosphonates: β-Co(3)(ImhedpH)(2)(H(2)O)(4)·2H(2)O (1), Co(3)(ImhedpH)(2)(H(2)O)(4) (2), and Mn(ImhedpH(2))·H(2)O (3). In compound 1, the columns made up of {Co1(2)O(2)} dimers and {PO(3)C} tetrahedra through corner-sharing are cross-linked through {Co2O(6)} octahedra, forming an inorganic layer. Neighboring layers are pillared by coordinated imidazole groups of ImhedpH(-) ligands, leading to a three-dimensional open framework containing two kinds of channels with sizes of 8.256 × 9.851 ? and 8.030 × 4.745 ? (van der Waals radii not accounted for). Compound 2 shows a layer structure, in which Co(3)(ImhedpH)(2)(H(2)O)(4) trimer units are connected through the corner-sharing of {Co1O(5)} trigonal bipyramids and {PO(3)C} tetrahedra, forming an inorganic layer containing 20-member rings composed of six Co atoms, two μ(3)-O1 units, and four O-P-O units. The noncoordinated imidazole groups protrude from two sides of the layer. Compound 3 shows a ladder structure, where the Mn(II) ions are bridged by ImhedpH(2)(2-) ligands through double O-P-O units to form a single chain, and two such chains are further fused together by sharing edges of {MnO(5)} trigonal bipyramids. The magnetic properties of 1-3 have been studied. Ferrimagnetism and field-induced magnetic transition from ferrimagnetism to a fully polarized state are observed in 1. Compounds 2 and 3 reveal dominant antiferromagnetic interactions between metal centers, and two-step field-induced magnetic phase transitions are found in 2.     

三维超分子配合物[Co2(Dpq)2(btec)(H2O)6]•2H2O的水热合成、晶体结构和电化学性质

以1,2,4,5-均苯四羧酸(btec)和二-吡啶-(3,2-d:2,3'-f)-二氮萘(Dpq)为混合配体,水热合成了一种三维超分子配合物: [Co2(Dpq)2(btec)(H2O)6]•2H2O (1), 并通过元素分析、红外光谱、热重分析和X-射线衍射法对其结构进行了表征。晶体结构解析结果表明,该配合物属单斜晶系,P21/c 空间群,晶胞参数为：a=0.8978(5)nm, b= 2.9822(16)nm, c= 0.7058(4)nm, β= 94.199(6)º, V= 1.8848(18)nm3, Z= 2, R1= 0.0350, wR2= 0.0796。该化合物由1,2,4,5-均苯四羧酸中羧基氧原子、二-吡啶-(3,2-d:2,3'-f)-二氮萘的螯合氮原子及水分子中氧原子与中心Co(II)离子配位, 形成六配位的扭曲八面体几何构型。羧酸作为桥连配体连接两个相邻的中心Co(II)离子形成钴配合物的双核单元,双核单元之间通过氢键及π-π堆积作用相互连接构成三维超分子网状结构。电化学实验结果表明,钴配合物修饰碳糊电极(1-CPE)在0.1 M 乙酸-乙酸钠缓冲溶液中电位范围+600 – –300 mV内有一对归属于Co(II)/Co(III) 的氧化还原峰,而且此修饰电极对亚硝酸根的氧化有很好的电催化效果。     

Hydrothermal Synthesis and Crystal Structure of a Zinc(Ⅱ)Coordination Polymer Assembled by Dpphen and H_2btec/btec

<正>A new metal-organic coordination polymer[Zn_2(dpphen)_2(H_2btec)(btec)_(0.5)]_n (dpphen=4,7-diphenyl-1,10-phenanthroline,H_4btec=1,2,4,5-benzenetetracarboxylic acid)1 was obtained via hydrothermal synthesis and characterized by elemental analysis,TG,IR spectrum and single-crystal X-ray diffraction.The complex crystallizes in the monoclinic system,space group P2_l/n with a=16.2996(14),b=14.3332(12),c=25.247(2)(?),β=103.4050(10)°,V=5737.7(9)(?)~3, C_(63)H_(37)N_4O_(12)Zn_2,M_r=1172.71,D_c=1.358 g/cm~3,μ(MoKα)=0.902 mm~(-1),F(000)= 2396,Z=4, the final R=0.0684 and wR=0.1281 for 3728 observed reflections(I2σ(I)).It exhibits a two-dimensional network structure constructed by mixed ligands of dpphen and H_2btec/btec.     

系列Co-M(M=Cd,Zn, Co)配位聚合物的合成、结构及光电性能

采用水热合成方法得到了3个Co-M配聚物: [CoCd(mal)₂(H₂O)₄]_n(1), [CoZn(mal)₂(H₂O)₄]_n(2) 和[Co₂(mal)₂(H₂O)₄]_n(3)(mal=malonate). 通过X射线单晶衍射确定了各配聚物的结构. 3个配聚物都是由丙二酸构筑并具有2D层状结构, 通过氢键进一步将2D层网联成3D无限网络结构. 通过表面光电压谱(SPS)对3个配聚物的表面光电性能进行了重点研究, 并与其相应的UV-Vis吸收光谱进行了对比. 结果表明, 这3个配聚物在300~600 nm范围内均表现出正的光伏响应, 而且SPS和UV-Vis光谱之间具有较好的对应关系.     

Synthesis and Characterization of Linked Clusters Capped by Alkylidyne

1 INTRODUCTION Constructing higher nuclearity clusters with well-defined dimensions and structures provide a rather active field of chemistry with potential applications in areas including nanotechnology, molecular recognition and catalysis[1~4]. A continuing effort has been directed toward developing a better methodology for systematic synthesis of supracluster compounds through molecular design [5,6]. On the basis of extensive investigation on the metal exchange reaction in cluster com…     

Structural evolution and magnetic properties of Co(II) coordination polymers varied from 1D to 3D constructed by 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene

Seven Co(II) coordination polymers, [Co(btx)(3)(H(2)O)(2)](ClO(4))(2)·(btx)·2H(2)O (1), [Co(btx)(3)(H(2)O)(2)](BF(4))(2)·(btx)·2H(2)O (2), [Co(btx)(2)(H(2)O)(2)](NO(3))(2)·2H(2)O (3), [Co(btx)(2)Cl(2)] (4), [Co(btx)(BA)(2)(H(2)O)(2)]·2HBA (5), [Co(btx)(IPA)] (6) and [Co(3)(btx)(3)(BTA)(2)(H(2)O)(2)] (7) (btx = (1,4-bis(1,2,4-triazol-1-ylmethyl)benzene), HBA = benzoic acid, H(2)IPA = isophthalic acid, H(3)BTA = benzene-1,3,5-tricarboxylic acid), have been hydrothermally synthesized and characterized. 1 and 2 are isostructural and show a 1D Co-μ(2)-btx-Co chain structure, in which btx acts as both a bridging and terminal ligand. 3 is also a 1D chain structure but different from 1 and 2. The Co(II) ions are bridged by double μ(2)-btx to form Co(2)-btx(2) rings, which were further connected into 1D chains by sharing the Co(II) ions of the rings. 4 exists as a 2D grid with (4,4) topology structure. When aromatic acid was introduced to the synthetic system, three other coordination polymers 5-7 were obtained. In 5, the 1D chain is as that of 1, except that the terminal ligand was replaced by BA(-). 6 shows a two-fold parallel interpenetration framework featuring a 6-c uninodal net with (3(3),4(6),5(5),6) Schlafli topological symbol. 7 is an interesting 3D framework, which contains a 2-nodal net motif with the unprecedented (3(6),4(2),5(6),6)(3(9),4(9),5(3))(2) topology structure. The influence of the varieties of the structures and magnetic properties are studied and discussed in detail.     

Construction of hydrogen-bonded and coordination-bonded networks of cobalt(II) with pyromellitate: synthesis,structures, and magnetic properties

Synthesis (hydrothermal and metathesis), characterization (UV-vis, IR, TG/DTA), single-crystal X-ray structures, and magnetic properties of three cobalt(II)-pyromellitate complexes, purple [Co(2)(pm)](n) (1), red [Co(2)(pm)(H(2)O)(4)](n) x 2nH(2)O (2), and pink [Co(H(2)O)(6)](H(2)pm) (3) (H(4)pm = pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid)), are described. 1 consists of one-dimensional chains of edge-sharing CoO(6) octahedra that are connected into layers via O-C-O bridges. The layers are held together by the pyromellitate (pm(4-)) backbone to give a three-dimensional structure, each ligand participating in an unprecedented 12 coordination bonds (Co-O) to 10 cobalt atoms. 2 consists of a three-dimensional coordination network possessing cavities in which unbound water molecules reside. This highly symmetric network comprises eight coordinate bonds (Co-O) between oxygen atoms of pm(4-) to six trans-Co(H(2)O)(2). 3 possesses a hydrogen-bonded sandwich structure associating layers of [Co(H(2)O)(6)](2+) and planar H(2)pm(2-). The IR spectra, reflecting the different coordination modes and charges of the pyromellitate, are presented and discussed. The magnetic properties of 1 indicate complex behavior with three ground states (collinear and canted antiferromagnetism and field-induced ferromagnetism). Above the Néel temperature (T(N)) of 16 K it displays paramagnetism with short-range ferromagnetic interactions (Theta = +16.4 K, mu(eff) = 4.90 mu(B) per Co). Below T(N) a weak spontaneous magnetization is observed at 12.8 K in low applied fields (H < 100 Oe). At higher fields (H > 1000 Oe) metamagnetic behavior is observed. Two types of hysteresis loops are observed; one centered about zero field and the second about the metamagnetic critical field. The critical field and the hysteresis width increase as the temperature is lowered. The heat capacity data suggest that 1 has a 2D or 3D magnetic lattice, and the derived magnetic entropy data confirm an anisotropic s(eff) = 1/2 for the cobalt(II) ion. Magnetic susceptibility data indicate that 2 and 3 are paramagnets.     

Heterometallic Cu/Co and Cu/Co/Zn complexes bearing rare asymmetric tetranuclear cores: synthesis, structures, and magnetic and catalytic properties toward the peroxidative oxidation of cycloalkanes

The three novel heterometallic complexes [CuCo(III)Co(II)(2)(MeDea)(3)Cl(3)(CH(3)OH)(0.55)(H(2)O)(0.45)](H(2)O)(0.45) (1), [CuCo(III)Zn(2)(MeDea)(3)Cl(3)(CH(3)OH)(0.74)(H(2)O)(0.26)](H(2)O)(0.26) (2), and [CuCo(III)Zn(2)(MeDea)(3)Cl(3)(DMF)] (3) have been prepared using a one-pot reaction of copper powder with cobalt chloride (1) and zinc nitrate (2, 3) in a methanol (1, 2) or dimethylformamide (3) solution of N-methyldiethanolamine. A search of the Cambridge Structural Database shows that the tetranuclear asymmetric cores M(4)(μ(3)-X)(μ-X)(5) of 1-3 represent an extremely rare case of M(4)X(6) arrays. The magnetic investigations of 1 disclose antiferromagnetic coupling in a Co(II)-Cu(II)-Co(II) exchange fragment with J(Co-Cu)/hc = -4.76 cm(-1), J(Co-Co)/hc = -2.76 cm(-1), and D(Co)/hc = +34.3 cm(-1). Compounds 1-3 act as precursors for the mild peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone with overall yields up to 23%. The synthetic and structural features as well as the thermogravimetric behavior and electrospray ionization mass spectrometry data are discussed.     

Reductions by titanium(II) as catalyzed by titanium(IV)

The cobalt(III) complexes, [(NH3)5CoBr]2+ and [(NH3)5CoI]2+ are reduced by Ti(II) solutions containing Ti(IV), generating nearly linear (zero-order) profiles that become curved only during the last few percent of reaction. Other Co(III)-Ti(II) systems exhibit the usual exponential traces with rates proportional to [Co(III)]. Observed kinetics of the biphasic catalyzed Ti(II)-Co(III)Br and Ti(II)-Co(III)I reactions support the reaction sequence: [Ti(II)(H20)n]2+ + [Ti(IV)F5]- (k1)<==>(k -1) [Ti(II)(H2O)(n-1)]2+ + [(H2O)Ti(IV)F5]-, [Ti(II)(H2O)(n-1)]2+ + Co(III) (k2)--> Ti(III) + Co(II) with rates determined mainly by the slow Ti(IV)-Ti(II) ligand exchange (k1 = 9 x 10(-3) M(-1) s(-1) at 22 degrees C). Computer simulations of the catalyzed Ti(II)-Co(III) reaction in perchlorate-triflate media yield relative rates for reduction by the proposed active [Ti(II)(H2O)(n-1)]2+ intermediate; k(Br)/k(I) = 8.     

A series of chiral coordination polymers containing helicals assembled from a new chiral (R)-2-(4'-(4'-carboxybenzyloxy)phenoxy)propanoic acid: syntheses, structures and photoluminescent properties

Ten new chiral coordination polymers, namely, [Ni(L)(H(2)O)(2)] (1), [Co(L)(H(2)O)(2)] (2), [Cd(L)(H(2)O)] (3), [Cd(L)(phen)] (4), [Mn(2)(L)(2) (phen)(2)]·H(2)O (5), [Cd(2)(L)(2)(biim-4)(2)] (6), [Zn(2)(L)(2)(biim-4)(2)] (7), [Cd(L)(pbib)] (8), [Cd(L)(bbtz)] (9) and [Cd(L)(biim-6)] (10), where phen = 1,10-phenathroline, biim-4 = 1,1'-(1,4-butanediyl)bis(imidazole), pbib = 1,4-bis(imidazole-1-ylmethyl)benzene, bbtz = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene, biim-6 = 1,1'-(1,6-hexanedidyl)bis(imidazole), and H(2)L = (R)-2-(4'-(4'-carboxybenzyloxy)phenoxy)propanoic acid, have been synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by infrared spectra (IR), powder X-ray diffraction (PXRD), elemental analyses and thermogravimetric (TG) analyses. Compounds 1 and 2 exhibit similar 1D left-handed helical chains, which are further extended into 3D supramolecular structures through O-H···O hydrogen-bonding interactions, respectively. Compound 3 shows a 2D double-layer architecture containing helical chains. Compound 4 features two types of 2D undulated sheets with helical chains, which are stacked in an ABAB fashion along the c direction. Compound 5 possesses a 1D double chain ribbon structure containing unusual meso-helical chains, which is linked by π-π interactions into a 2D supramolecular layer. These layers are further extended by hydrogen-bonding interactions to form a 3D supramolecular assembly. Compounds 6 and 7 are isostructural and exhibit 2D (4(4))-sql networks with helical chains. Neighboring sheets are further linked by C-H···O hydrogen-bonding interactions to generate 3D supramolecular architectures. Compounds 8-10 are isostructural and display 3D 3-fold interpenetrating diamond frameworks with helical chains. The effects of coordination modes of L anions, metal ions and N-donor ligands on the structures of the coordination polymers have been discussed. The luminescent properties of 3, 4 and 6-10 have also been investigated in detail.